As a technique for correcting the current position of a vehicle detected by a position measurement device, proposed is a technique that corrects the position of a vehicle by finding the distance from the vehicle to an intersection using a camera mounted on the vehicle and then identifying the position of the vehicle relative to the intersection in map information (see Japanese Patent Application Publication No. Hei 9-243389).
The technique described in Japanese Patent Application Publication No. Hei 9-243389, however, may not be able to correct the current position of a vehicle in situations where it is difficult to detect an intersection, such as when the vehicle is travelling on an expressway.